质量数A≈125的热核GDR特性的研究

简单介绍了利用LNS的回旋加速器产生的116Sn束轰击12C和24Mg靶的实验装置以及实验过程.该实验通过MEDEA探测器测量了由全熔合与非全熔合反应产生的较低激发能区(160—300MeV)质量数A≈125的热核的巨偶极共振特性,比较了不同靶子、不同束流能量时巨偶极共振的γ产额的变化

A signal of spinodal decomposition around Fermi energy.

none25Using thermal photons to tag the reaction time a prompt IMF emission component has been identified in central Ni-58 + (197)An collisions at 45 MeV/amu. The comparison with theoretical calculations supports the hypothesis of dynamical emission in the spinodal regionnoneR. Alba;C. Agodi;C. Maiolino;A. Del Zoppo;M. Colonna;G. Bellia;R. Coniglione;P. Finocchiaro;K. Loukachine;E. Migneco;P. Piattelli;D. Santonocito;P. Sapienza;M. Bruno;M. D'Agostino;M.L. Fiandri;G. Vannini;N. Colonna;F. Gramegna;P.F. Mastinu;I. Iori;A. Moroni;G.V. Margagliotti;P.M. Milazzo;R. RuiR. Alba;C. Agodi;C. Maiolino;A. Del Zoppo;M. Colonna;G. Bellia;R. Coniglione;P. Finocchiaro;K. Loukachine;E. Migneco;P. Piattelli;D. Santonocito;P. Sapienza;M. Bruno;M. D'Agostino;M.L. Fiandri;G. Vannini;N. Colonna;F. Gramegna;P.F. Mastinu;I. Iori;A. Moroni;G.V. Margagliotti;P.M. Milazzo;R. Ru

The reaction entrance channel and isotopic composition of fragments in a dynamical and statistical multifragmentation regime.

From the study of the Ni+Ni,Ag 30 MeV/nucleon dissipative midperipheral collisions, it has been possible to detect events in which Intermediate Mass Fragments (IMF) are emitted by two different sources with different mechanisms. The sources are: a) a quasi-projectile (QP) (and a quasi-target (QT)), with an excitation energy that leads to multifragmentation totally described in terms of a statistical disassembly of a thermalized system (T <IMG SRC="/img/revistas/bjp/v34n3a/a59img01.gif">4. MeV, E*<IMG SRC="/img/revistas/bjp/v34n3a/a59img01.gif"> 4 MeV/nucleon); b) an intermediate source, emitting both light particles and IMF. In this second case, fragments are more neutron rich than the average matter of the overall system, and have a very different charge distribution, with respect to those statistically emitted from the QP. The above features can be considered as a signature of the dynamical origin of the midvelocity emission. The results of this analysis show that IMF can be produced via different mechanisms simultaneously present within the same collision. They also show that the probability of IMF production via dynamical reaction increase with the size of the target nucleus

Long-term measurement of acoustic background in very deep sea

The NEMO (NEutrino Mediterranean Observatory) Collaboration installed, 25 km E offshore the port of Catania (Sicily) at 2000 m depth, an underwater laboratory to perform long-term tests of prototypes and new technologies for an underwater high energy neutrino km3-scale detector in the Mediterranean Sea. In this framework the Collaboration deployed and successfully operated for about two years, starting from January 2005, an experimental apparatus for on-line monitoring of deep-sea noise. The station was equipped with four hydrophones and it is operational in the range 30 Hz–43 kHz. This interval of frequencies matches the range suitable for the proposed acoustic detection technique of high energy neutrinos. Hydrophone signals were digitized underwater at 96 kHz sampling frequency and 24 bits resolution. The stored data library, consisting of more than 2000 h of recordings, is a unique tool to model underwater acoustic noise at large depth, to characterize its variations as a function of environmental parameters, biological sources and human activities (ship traffic, etc.), and to determine the presence of cetaceans in the area